Process for the electrolytic production of metals



H. L. SLATIN Oct. 10, 1961 PROCESS FOR THE ELECTROLYTIC PRODUCTION OF METALS Filed Jan. 8, 1959 2 Sheets-Sheet 1 INVENTOR. Hague-y L. SLAr/N ,4 rro gm 7 Oct. 10, 1961 H. L. SLATIN 3,003,934

PROCESS F OR-THE ELECTROLYTIC PRODUCTION OF METALS Filed Jan. 8, 1959 2 Sheets-Sheet 2 Ha. um Eco/1:1,:

L/FI' MEMA/wsn B1 l/n I un T, O Pee-s5 so Saucs HELIUM INVENTOR. Hague-y L SLAT/ly ,4 rroezvey 3,003,934 i atented Oct. 10, 1961' 3,003,934 PRDCESS FOR THE ELECTROLYTIC PRODUC- TION F METALS Harvey L. Slatin, New York, N.Y., assignor to Timax Associates, New York, N.Y., a partnership of New York Filed Jan. 8, 1959, Ser. No. 785,597 28 Claims. (Cl. 204-6 4) This invention relates to the electrolytic production of pure metals from their oxides and particularly titanium metal from its oxides and other oxygen compounds.

The present application is a continuation-in-part of my applications Serial Numbers 225,375 (now Patent No. 2,864,749), 383,762 and 493,442; filed May 9, 1951, October 2, 1953 and March 10, 1955, respectively, for processes for the production of titanium metal. Application Serial No. 493,442 is now abandoned.

It is a primary object of this invention to provide a process for the production of group IV metals from their respective oxides of suflicient purity and in such crystalline form and character so as to be useful as an anode feed material in the production of very pure and ductile metal by means of electrorefining.

This invention relates particularly to the electrolytic production of high purity and ductile metals of the group titanium, zirconium and hafnium from their oxides and other oxygen compounds and particularly relates to a process for producing these metals from their oxides by electrolysis in a form and composition such that they are readily adaptable to electrorefining.

It is a primary object of this invention to provide a continuous and practical electrolytic process for the production of substantially pure and ductile titanium of large crystalline size, in a sintered' or semi-fused state, from titanium oxides.

Although this specification may refer principally to titanium, it is understood that the process applies equally well to the sister elements zirconium and hafnium.

Dr. Wilhelm Borchers and Wilhelm Huppertz developed a process for the production of titanium by the electrolysis of oxygen compounds of titanium added to water soluble alkaline earth halides (German Patent 150,557 issued April 27, 1904). The product they obtained by their batch process was described as a powdered metal mud or sludge of inferior purity, contaminated with titanium oxides. The powdered metal mud or sludge was described as being dispersed throughout the solid mass, requiring reprocessing of the frozen and leached electrolyte after each run. The separation of salts, titanium oxides and other contaminants from the metal, as described, appears to be elaborately involved and was stated to be an incomplete separation.

Accordingly, it is a further object of this invention to provide a continuous electrolytic process for the production of substantially pure and ductile titanium of large crystalline size which is readily recoverable from its adherent electrolyte.

These and other objects are achieved in the practice of this invention by providing an electrolyte composed of alkaline earth halides in combination with alkaline earth oxides as a solvent. This essential electrolyte in some manner metamorphoses the dioxides of titanium, zirconium or hafnium so that these dioxides are directly reduced to metal. The metal crystals produced are readily recovered and are suitable for refining.

It is a further object of this invention to provide a continuous electrolytic process for the production of substan tially pure and ductile titanium of large crystalline size from its other oxygen compounds such as the calcium titanate.

Other objects and advantages will appear from the following specification taken in connection with the accompanying drawings depicting a general form of apparatus operating in accordance with this invention.

The reduction of titanium oxides is a stepwise process proceeding from the tetravalent to trivalent to divalent to metal, the steps depending on the presence of dioxide, sesquioxide, or monoxide in the electrolyte or feed material. Titanium metal at the temperature of electrolysis can react with oxygen and oxygen containing compounds, including the various oxides of titanium, and thereby contaminate the deposited titanium metal. Consequently, in the electrolysis of titanium oxides and other oxygen compounds to produce titanium metal as herein described and wherein the cathode is depended from above, it has been found that the following conditions must be imposed on the process if production of substantially pure and ductile titanium in large crystalline size is to be attained.

(A) In order to minimize secondary reactions, itis necessary to isolate the anode and cathode areas from each other by appropriate baffling and compartmentalizing of the cell. For example, the anode gases, 0 CO, and CO must be kept from reacting with the cathode product and the migration of reduced, i.e. lower valent, titanium ions between the catholyte and the anolyte must be restricted.

(B) The atmosphere surrounding the cathode and in contact with the catholyte must be purified and dry inert gas, such as helium or argon.

(C) The cations in the solvent must be more electropositive than titanium in its lowest valent state. At the preferred temperatures of operation, calcium compounds alone are preferred as solvents, but at lower temperatures strontium salts may also be added.

(D) The electrolyte must not contain any undissolved oxides.

(E) The temperature of the electrolyte in the active portion of the cell must be maintained above its melting point.

(F) A high temperature must be maintained at the cathode-deposition surface for the production of a cathode deposit which will contain metal in a dense mass, having a minimum of included salts, have a low dragout ioss, and be easy to handle.

(G) The current density at the cathode-deposition surface must be high enough to produce metal of massive crystalline form.

(H) The anode current density should be kept low enough to prevent co-deposition or liberation of chlotime at the anode.

(I) The cathode deposit may be withdrawn at a rate designed to maintain uniform cathode current densities and preserve the condition set forth in (G) and explained later.

(I) The hot cathode deposit must be withdrawn into a non-contaminating atmosphere such as a chamber filled with purified and dried inert gas wherein the deposit can be cooled below a temperature at which the deposit will react with oxygen, nitrogen or moisture.

In the accompanying drawings illustrating one manner or" the processing by typical equipment FIG. 1 is a partial vertical cross sectional View of a cell; and

FIG. 2 is a similar view illustrating diagrammatically the recycling of the electrolyte of FIG. 1 as applied to a cell as illustrated in FIG. 1.

Referring to FIG. 1 of the drawings, there is shown, partly in cross section and somewhat diagrammatically, an electrolytic cell generally indicated at 10 having a heat resistant outer metal shell 11, preferably made of corrosion resistant material such as nickel or Inconel, enclosing the side walls and bottom and fitted with a top flange 12 to which is tightly bolted a metal cover 14 provided with a gasket 15. The bottom and sides of the shell are lined with several layers of heat insulating material. For example, an outer layer 16 of silica brick, an adjacent layer 18 of alumina or magnesia brick and an inner layer '19 of titania, calcium oxide or alumina brick may be used. The underside of the cover 14 should also be protested by a lining 2t; of refractory material such as alumina or other material. The cavity within the cell contains, as hereinafter described, an electrolyte 21, a portion of which is kept preferably in frozen condition forming a lining 22 for the Walls and bottom of the cell. The heat insulating walls of the cell may, if desired, by provided with suitable means for water cooling. Centrally disposed in the cell is a water cooled compartmentalizing cylinder 24 having an inner wall 25 and an outer wall 26 and a coolant inlet 28 and outlet 29. Cylinder 24 is supported on cover 14, extending through a central opening therein, by a circumferential flange 30 which is electrically insulated from cover 14 by a suitable spacer 31. Cylinder 24 is of such size as to extend a short distance below the surface of electrolyte 21. Mounted on top of cylinder 24 is an enclosure 32 for a gate valve 34 which is used to close off me cathode compartment 35 from the cooling chamber 3? The valve is operated by a handle 36. Supported on the valve housing 32 is an upper water-jacketed cooling chamber 38 having a coolant inlet 39 and outlet 40. The chamber 33 is provided with a welded flange 41 containing a gas inlet 42 and a gas outlet 44. The opening in flange 41 is co-extensive with the inner wall of chamber 38. Mounted on flange 41 and electrically insulated therefrom by a plate 45 of Transite or other suitable material is a packing gland 46 through which the cathode 43 extends. The upper end of the cathode is provided with means for making the usual electrical connections and is attached to mechanism (not shown) for raising or lowering it. The cathode may be water cooled in any known fashion. Also carried by cover 14 are a plurality of anodes 43 which are supported in suitable gastight packing glands 50 mounted on electrically insulating slabs 51 of Transite or the like. The anodes 49 are preferably arranged symmetrically around the outer portion of the cell and several, for example four or more, may s used. leans for cooling the ends of the anodes and their mountings above the cover may be provided if desired. Suitable means (not shown) are provided for taking power connections to the anodes. Cover 14 is provided with one or more gas vents 52 communicating with the anode chamber 53 which is that portion of the cell r' side of the cylinder 24 above the electrolyte 21. Extending through the wall of the compartmentalizing cylinder 24 is a feed port 54 which communicates with the outside of the cell and through which material may be introduced into the cathode compartment 35.

Thee cathode 48 is preferably made of titanium but may be made of another suitable metal such as iron, nickel, moiybdcnum or tungsten. Before being introduced into the chamber 35 through gland 46 it is carefully cleaned and dried.

The anodes 49 are made of carbon, and a grade of particularly dense graphite ispreferred, for example, AGR grade graphite made by National Carbon Co. has been found satisfactory.

As above stated, calcium compounds are preferred as the solvent in the electrolyte. Under some special conditions and at lower temperatures strontium salts may be present. As examples. eutectic compositions of the following solvents have been used: 1) 74.44 mol percent CaCl -lZ.3 mol percent CaF -l3.26 mol percent 0210, melting about 795 C.; and (2) 65 mol percent CaCl -JS mol percent SrCl plus about 15% by weight CaG cr SrO, melting at about 646 C. A preferred solvent, however, is a eutectic solution of 89.77 mol percent CaCl lO.23 mol percent CaO, melting at about 727 C. It is to be noted that the presence .of CaO facilitates the solutinrt of T10 and other titanium oxides. All of the 4 components of the preferred bath are sufiiciently water soluble and the cations are more electropositive than titanium at the temperature of operation, as hereinafter described.

The raw material feed is preferably titanium dioxide.

ther oxides such as TiO, Ti O calcium titanate and calcium titanite may be employed. The dioxide or other titanium compounds above mentioned are carefully dried and may be added to the catholyte directly. None of these titanium compounds is very soluble in the solvents mentioned, and hence their quantity in the bath is kept below the point where any undissolved titanium compounds would be present, less than 3% by weight, for example. Their presence would contaminate the product by mechanical inclusion and they would be difficult to remove therefrom because they are not water soluble. As the oxides are reduced to metal at the cathode, the electro lyte becomes depleted and must be replenished to maintain adequate metal ion concentrations in the vicinity of the cathode. This may be done continuously by passing the depleted solution from the cathode chamber to a mother liquor tank, for example through an outlet pipe 55, enriching it and passing the enriched electrolyte back into the cathode chamber through inlet 54. The entire circulating system is closed to the atmosphere and maintained at the same temperature as the cell by appropriate heating means.

Recirculation of the electrolyte may be by means of a helium gas lift as shown in FIG. 2. Dry pure helium gas is fed through inlet pipe 69 which enters chamber 61 through a side wall. The helium outlet pipe 64 is centrally located in a larger pipe 67 having an inlet skirt 70 of larger diameter centrally placed within the chamber 61 containing electrolyte and raw material feed 72 in the form of pressed TiO slugs fed to the chamber 61 from time to time via inert gas lock 73. The smaller solid particles of TiO are prevented from entering the electrolyte stream by skirt 70 and sieve plate 76. The undissolved TiO is accumulated in the bottom of chamber 61 and may be drained through blow-down valve 77. Helium gas enters by pipe 60 and carries enriched electrolyte through the short height represented by the linear distance from the electrolyte level 78 in chamber 61 and outlet 80. The level of the electrolyte in cell 1'0 and the level 78 are substantially the same. In space 82, the helium gas and the fused electrolyte are separated; the helium passes through holes 84 in batfle plate 85 and may be recycled by a pump re-entering inlet pipe 60. The fused electrolyte rises in dip-leg 86 and overflows entering the cell by means of inlet pipe 54 scaled by gland 83. Safety overflow tube 89 provides for equating the pressure in the system and for taking care of large excesses of feed. The depleted electrolyte enters outlet pipe 55 and flows to chamber 61 by gravity. As the depleted electrolyte passes over the TiO, it becomes enriched with the lower oxide by solution.

The operation of the above described cell is as follows: The requisite amount of molten solvent consisting of a eutectic melt of CaCl and C210 is prepared in the mother liquor tank and enriched by the addition of the raw material to be employed preferably not in excess of 3% TiO by weight. Any volatile matter or moisture is driven off at this stage and the electrolyte is fed into the cell 10 to the desired level. This level is maintained constant in any suitable way. The cathode chamber 35 is then filled and continuously flooded with inert pasv preferably argon which has been purified and dried. This gas may be recycled. By reason of the cooling of the cylinder 24 a frozen ring of salt 56 forms thereon which extends into the electrolyte 21, effectively increasing the depth of the bafiie and protecting the cylinder 24 from chemical or electrolytic attack. The frozen salt lining 22 forms simultaneously on the bottom and sides of the cell. Cathode 48 is lowered into contact with the bath and electrolysis is commenced. The cell is operated long enough at this stage to remove by deposition on the cathode all of those.

elements whose decomposition potentials are less than those of titanium. These deposits are removed from the cathode and discarded. A fresh cathode is inserted into contact with the bath, the proper DC current applied, the electrode withdrawal mechanism is started and the production of titanium commences. The withdrawal of the titanium from the bath as it is formed is done at such a rate as is calculated to maintain the cathode current density substantially constant. It permits drainage of salt back into the bath and it also removes the titanium from the sphere of contaminants in the bath, for instance, the titanium oxides present. After a body of titanium of the desired length has been produced 3 or more inches, for example, the cathode is drawn into the upper gasfilled chamber 38, the current turned off and valve 34 is closed. The titanium on the cathode is retained in chamber 38 in an inert atmosphere untilit is cooled and may be removed into the air without contamination by reacting with oxygen, nitrogen or moisture. The cathode is then removed and replaced by a fresh cathode and the cycle repeated.

The temperature of the electrolyte is maintained sufiiciently above its normal melting point to insure liquidity in the active portion of the cell. It is preferred to operate in the active portion of the electrolyte 21 in the vicintiy of 1000 C., although temperatures as high as 1250" C. have been used without ill effects.

Initial cathode current densities are preferably maintained in excess of about 30 amperes per square inch and have been carried as high as 100 amperes per square inch. This gives a very high temperature at the inter-' face between the salt and the deposited metal, approaching the melting point of titanium to promote sintering or incipient fusion of the deposit. Such deposits have analyzed in excess of 99% pure, for example 99.2 and 99.6.

The nature of the invention is further illustrated in the following additional examples.

Example I Using a covered graphite lined crucible as an electrolytic cell, fused CaCl under a dry HCl atmosphere. After fusion, bubbled dry HCl gas through the melt to rid the bath of moisture and prevent hydroylsis. Electrolyzed the melt under low voltage under argon to remove residual moisture and impurities. When the bath is properly conditioned in this fashion, a strip of titanium will not react in the melt when submerged therein. Added precalcined 200 mesh TiO to the melt and stirred. Very little if any TiO was soluble therein. Added TiO to make about a 3% mix by weight (calculated). The graphite crucible was made anode to a centrally disposed nickel cathode immersed in the electrolyte. Electrolyzed the bath for about 4 hours under argon. During the electrolysis added TiO to the bath to replace that calculated to be consumed. The cathode current density was initially calculated to be about 28 amperes per square inch. The anode current density was below 1 ampere per square inch as calculated. The temperature was Example II Repeated the experiment cited above except the pre- The bath was allowed to freeze The mass, about 600 7 calcined CaO was added to the purified melt before adding the TiO;,. About a 6% calcium oxide solution was used. The temperature was about 900 C. Precalcined TiO was added to the melt and a 3% solution was '0' tained. Commenced electrolysis and this time it was apparent that titanium was depositing. The electrolysis was continued for about 8 hours, TiO was added to the bath from time to time to maintain the titanium concentration in the bath. The anode current was less than 10 amperes per square inch and the initial cathode current density was calculated to be about 30 amperes per square inch. After the electrolysis was completed, the salts were dissolved in' water. The electrode product was treated with dilute HCl to facilitate solution of the CaO, etc., and dried in air Without heat. The product was composed of bright silvery crystals of titanium. X- ray analysis showed titanium metal present and there was no evidence of lower oxides of titanium.

The deposit was readily separated from the electrolyte and was in large crystalline form. This material was adaptable in form and purity to electrorefining and titaniurn of 99.9+% was prepared therefrom.

Example III The experiment of Example 11 was repeated using ZrO in place of the TiO The concentration of CaO was nearly 16% by weight and the current densities and temperature used were substantially the same. The duration of electrolysis of the Zr0 was about eight hours. The product was separated from the melt as described above. X-ray analysis showed the presence of Zirconium metal and no oxides or carbides of zirconium could be detected. The crystalline form and size and purity of the deposit was such that this material lends itself admirably to electrorefining The process of the invention may be carried out in many ways provided that the following conditions are observed:

The electrolyte solvent may consist of those elements whose cations are more electropositive with respect to halogens and oxygen than those of titanium. The alkaline earth metals calcium and strontium are preferred. Of the halides, the chloride is the preferred constituent. The ratio of calcium (or strontium) oxide to chloride in the melt is not critical and may be varied from a feW percent to about 25%. However, a substantial amount of oxide must be present to give the desired results.

Although any solute oxide may be used in the process, the dioxide is preferred as it is cheaper and readily purified.

All the ingredients in the electrolyte must be anhydrous and free of water. Moisture stiifens the electrolyte and may induce inoperability.

The concentration of TiO in the electrolyte may be varied from a few tenths of a percent to about 5%. One should be careful to avoid excessive additions of solute beyond the solubility limit, as no good purpose is served by such practice and there is a possibility of transferring oxide particles mechanically to the product.

The temperature of the electrolysis may be varied over a wide range from about 700 C. to about 1100 'C. However, temperatures below 850 C. are preferred.

The anode current density should be kept below 10 ampers per square inch. The preferred anode current density is below 6 amperes per square inch.

The cathode current density may be varied over a wide range with good results. Although fractions of an ampere to nearly amperes per square inchhave been used, the preferred range lies between 10 and 30 amperes per square inch.

The cathode material preferred is the element to be deposited, but good results are obtained with nickel, Inconel and the like. The anodes may be carbon or graphite, and dense graphite is preferred.

Since many Widely differing embodiments of this in- 7 vention will occur to one skilled in the art, it is to be understood that it is not limited to the specific details above illustrated and described, and that various changes may be made therein without departing from the spirit of the invention as defined in the appended claims.

I claim:

1. An electrolytic process for the production of a metal of the group IVB metals in excess of 99% purity and in the form of large, high purity crystals of metal comprising a fused electrolyte consisting essentially of a few percent of at least one alkaline earth oxide and at least one halide of the group of alkaline earth halides forming a high proportion of the electrolyte maintaining separation of the catholyte from the anolyte, providing at least an efiective amount of one oxide of the multioxides of the group IVB metals in the catholyte compartment to deposit the group IVB metal on the cathode, maintaining the temperature of the bath above the melting point to insure complete solution of the metal oxide and to impart desired fluidity tothe solution, electrolyzing the electrolyte between a solid anode and a solid cathode with high cathode current density to deposit the group IVB metal on the cathode as large crystals of metal at a purity in excess of 99%.

2. A process for the production of a metal of the group IVB metals as set forth in claim 1 wherein said fused electrolyte comprises calcium oxide, calcium chloride and said multioxide of the group IVB metal.

3. A process for the production of a metal of the group IVB metals as set forth in claim 1 wherein the metal is titanium and its oxide is the dioxide.

4. A process for the production of a metal of the group IVB metals as set forth in claim 1 wherein the metal is zirconium and its oxide is the dioxide.

5. A process for the production of a metal of the group IVB metals as set forth in claim 1 wherein the metal is hafnium and its oxide is the dioxide.

6. A process for the production of a metal of the group IVB metals as set forth in claim 1 wherein the ratio of calcium oxide to calcium chloride is 1:6.

7. A process for the production of a metal of the group IVB metals as set forth in claim 1 wherein the cathode current density lies between 5 and 30 amperes per square inch.

8. A process for the production of a metal of the group IVB metals as set forth in claim 1 wherein the temperature of electrolysis lies between 700 and 1100 C.

9. A process for the production of a metal of the group IVB metals as set forth in claim 1 wherein the concentration of the solute in the electrolyte lies below about 5 weight percent.

10. An electrolytic process for the production of a metal of the group IVB metals in crystalline form of a purity for subsequent use as an anode feed for electrorefining to a purity in excess of 99% comprising a fused electrolyte consisting essentially of a few percent of at least one alkaline earth oxide and at least one halide of the group of alkaline earth halides forming a high proportion of the electrolyte and containing at least an effective amount of one oxide of the multioxides of the group IVB metals to deposit the group IVB metal on the cathode, maintaining the temperature of the bath above the melting point to insure complete solution of the metal oxide and to impart desired fluidity to the solution, electrolyzing the electrolyte between a solid anode and a solid cathode with a high current density to deposit the group IVB metal on the cathode in crystalline form for subsequent electrorefining to high purity metal.

11. A process for electrolytic production of titanium metal in excess of 99% purity and in the form of large, high purity crystals of ductile metal comprising completely dissolving a lower valent oxide of said metal in a fused salt bath composed of a solvent mixture of calcium chloride and calcium oxide and maintaining separation of the catholyte from the anolyte, maintaining the temperature of the bath above the melting point to insure complete solution of said oxide and to impart desired fluidity to the solution, feeding said solution free of undissolved oxides to said catholyte compartment only, maintaining high cathode current density of at least fifty ampere-s per square inch to attain a deposit of the metal as large crystals of ductile metal at a purity in excess of 99%, and simultaneously progressively withdrawing the cathode and accumulating deposit from the catholyte into a cooling, inert, non-contaminating atmosphere and cooling and cleaning said removed deposit.

12. A process for electrolytic production of a metal as set forth in claim 11 in which the cathode with its deposit is withdrawn at a. rate maintaining uniform cathode current densities.

13. A process for the electrolytic production of titanium metal comprising providing an electrolyte consisting of a complete solution of lower valent oxide of titanium in a fused salt bath of calcium chloride and oxide with anode surfaces in an anolyte chamber and cathode surfaces in a catholyte chamber separating the catholyte from the anolyte, subjecting said electrolyte to electrolysis between the anode and cathode surfaces at a cathode surface density sufficiently high to deposit titanium in the form of large crystals of substantially pure and ductile titanium in an inert atmosphere on the cathode surfaces, and continuously withdrawing said cathode surfaces with the accumulating deposit from the contaminating oxides in the electrolyte, and passing the cathode and deposit into an inert gaseous atmosphere of the group consisting of helium and argon.

14. A process for the electrolytic production of titanium metal as set forth in claim 13 in which the dissolved titanium oxide is TiO.

15. A process for the electrolytic production of titanium metal as set forth in claim 13 in which the cathode current density is greater than fifty amperes per square inch.

16. A process for the electrolytic production of titanium metal as set forth in claim 13 in which the temperature of the electrolyte is about 1000" C. to 1250 C.

17. A process for the electrolytic production of titanium metal as set forth in claim 13 in which the catholyte is separately prepared and continuously re-cycled.

18. A process for the electrolytic production of titanium metal as set forth in claim 13 in which the electrolyte solvent is CaCl and CaO.

19. A process for the electrolytic production of titanium metal as set forth in claim 18 in which the concentration of the titanium oxides in the electrolyte solution is less than 3% by weight.

20. A process for the continuous electrolytic production of titanium metal of a purity in excess of 99% in the form of large crystalline masses comprising providing a molten electrolyte of calcium chloride and calcium oxide in an electrolytic cell compartmentalized into an anolyte chamber and a catholyte chamber, feeding to said cathode chamber only a complete solution of an oxide of titanium free of undissolved oxide, subjecting said electrolyte and said solute solution to electrolysis under an inert gas atmosphere between an anode immersed in said anolyte and a cathode immersed in said catholyte, maintaining a substantially constant high cathode current density at said cathode to deposit titanium metal at said cathode, and recovering said deposited titanium by withdrawing said cathode into an inert gas atmosphere.

21. A process for the continuous electrolytic production of titanium metal as set forth in claim 20 wherein the depleted catholyte liquor is separately prepared and continuously re-cycled.

22. A process for the continuous electrolytic production of titanium metal as set forth in claim 20 wherein 9 the cathode current density is in excess of 50 amperes per square inch.

23. A process for the continuous electrolytic production of titanium metal as set forth in claim 20 wherein the temperature of the electrolyte is maintained in the vicinity of 1000 C.

24. A process for the continuous electrolytic production of titanium metal as set forth in claim 20 in which the dissolved oxide of titanium is TiO.

25. A process for the continuous electrolytic production of titanium metal as set forth in claim 20 in which the cathode current density is maintained substantially constant by the continuous withdrawal of said cathode from the electrolyte.

26. A process for the continuous electrolytic production of titanium metal as set forth in claim 20 in which the solute concentration of TiO in the electrolyte is less than 3% by weight.

27. An electrolytic process for the production of a metal of the group IVB metals in crystalline form of a purity for subsequent use as an anode feed for electrorefining to a purity in excess of 99% comprising a fused electrolyte consisting essentially of a few percent of at 20 1,396,919 Brace Nov. 15, 1921 2,707,169 Steiuberg et a1 Apr. 26, 1955 2,845,386 Olson July 29, 1958 least one alkaline earth oxide and at least one halide of the group of alkaline earth halides forming a high propoition of the electrolyte and containing at least an effective amount of the dioxide of the group IVB metals to deposit the group IVB metal on the cathode, maintaining the temperature of the bath above the melting point to insure complete solution of the metal oxide and to impart desired fluidity to the solution, electrolyzing the electrolyte between a solid anode and a solid cathode with a high current density to deposit the group IVB metal on the cathode in crystalline form for subsequent electrorefining to high purity metal.

28. An electrolytic process as set forth in claim 27 wherein the group IVB metal is titanium and the dioxide is titanium dioxide.

References Cited in the tile of this patent UNITED STATES PATENTS 

1. AN ELECTROLYTIC PROCESS FOR THE PRODUCTION OF A METAL OF THE GROUP IVB METALS IN EXCESS OF 99% PURITY AND IN THE FORM OF LARGE, HIGH PURITY CRYSTALS OF METAL COMPRISING A FUSED ELECTROLYTE CONSISTING ESSENTIALLY OF A FEW PERCENT OF AT LEAST ONE ALKALINE EARTH OXIDE AND AT LEAST ONE HALIDE OF THE GROUP OF ALKALINE EARTH HALIDES FORMING A HIGH PROPORTION OF THE ELECTROLYTE MAINTAINING SEPARATION OF THE CATHOLYTE FROM THE ANOLYTE, PROVIDING AT LEAST AN EFFECTIVE AMOUNT OF ONE OXIDE OF THE MULTIOXIDES OF THE GROUP IVB METALS IN THE CATHOLYTE COMPARTMENT TO DEPOSIT THE GROUP IVB METAL ON THE CATHODE, MAINTAINING THE TEMPERATURE OF THE BATH ABOVE THE MELTING POINT TO INSURE COMPLETE SOLUTION OF THE METAL OXIDE AND TO IMPART DESIRED FLUIDITY TO THE SOLUTION, ELECTROLYZING THE ELECTROLYTE BETWEEN A SOLID ANODE AND A SOLID CATHODE WITH A HIGH CATHODE CURRENT DENSITY TO DEPOSIT THE GROUP IVB METAL ON THE CATHODE AS LARGE CRYSTALS OF METAL AT A PURITY IN EXCESS OF 99%. 